Nematodes I: Filarids Flashcards
What order are filarids in?
Spirurida
What kind of life cycle do spirurids have?
Indirect life cycles
What are the intermediate hosts of filarids?
Blood sucking arthropods
Describe the vermiform embryo of filarids
Contains only-cell clusters as primordia
Pre-L1 stages
Ingested by IH
L1 to L2 to L3 in IH
When do filarids have clearly recognizable organs?
L1
What is microfilariae an example of?
Vermiform embryo
What is the definitive host of Onchocerca cervicalis?
Equids
What is the intermediate host of Onchocerca cervicalis?
Culicodes spp
What is the Onchocerca cervicalis life cycle?
L3 infects DH with next blood meal of IH
L3, L4, and adults are in the nuchal ligament
Microfilariae in subdermal connective tissue
Where are Onchocerca cervicalis microfilaria?
Widely distributed in dermis
Other subdermal connective tissues
Ocular conjunctivae
Where are Onchocerca cervicalis larvae?
Nuchal ligament
Where are the Onchocerca cervicalis adults?
Often unnoticed
Woven into the deep connective tissue in the nuchal ligament
What is onchocercal dermatitis cause by?
Antigen release from dying microfilaria
How do you diagnose Onchocerca cervicalis?
Skin biopsy
What is the differential for Onchocerca cervicalis?
Hypersensitivity to biting flies
What is the definitive host of Onchocerca lupi?
Dogs and cats
What is Onchocerca lupi the causative agent of?
Canine onchocercosis
Acute and chronic ocular disease
What causes patent infections with Onchocerca lupi?
Large numbers of microfilaria
What are the signs associated with canine onchocercosis?
Conjunctivitis Discomfort Periorbital swelling Exophthalmos Photophobia Lacrimation Dischrage Periocular tissue Granulomatous nodules Cysts
What is the definitive host of Acanthocheilonema reconditum?
Dogs
What are the intermediate hosts of Acanthocheilonema reconditum?
Fleas (Ctenocephalides felis, C. canis, Pulex iriitans)
Where is Acanthocheilonema reconditum microfilaria found?
In blood
Is Acanthocheilonema reconditum pathogenic or nonpathogenic?
Nonpathogenic
What is Acanthocheilonema reconditum an important differential of?
Dirofilaria immitis, which is pathogenic
What is the genus and species of heartworms?
Dirofilaria immitis
What is the DH of Dirofilaria immitis?
Domestic dog is the most prevalent
Domestive cat
Ferrets (rare)
What are the dead-end hosts of Dirofilaria immitis?
Bears
Raccoons
Beavers
Humans
In humans, what can Dirofilaria immitis be misinterpreted as?
Neoplasia
What is the IH of Dirofilaria immitis?
Mosquitoes
What are the reservoir hosts of Dirofilaria immitis?
Red wolf
Grey fox
Red fox
Coyote
What is the Dirofilaria immitis life cycle in a dog?
Mosquito takes a blood meal (L3 enters skin)
L4 migrate toward thorax, circulatory system
Adults in pulmonary arteries and right heart
Female produces microfilariae
Mosquito takes a blood meal
L1
L2
L3 migrate to mouth parts
What are the required hosts of Dirofilaria immitis?
Definitive host (susceptible population)
Intermediate host (susceptible mosquito species)
Reservoir hosts
Stable mosquito population (Anopheles spp., Aedes spp., Culex spp.)
What is the pathology if there is a higher worm burden?
More severe heart/lung disease
What are the early pathologic changes with heartworm?
Due to inflammatory processes in/around arteries of lower lungs
What are the late pathologic changes with heartworm?
Heart may enlarge and become weakened due to increased workload
Congestive heart failure
What happens to very active/ working dogs with heartworms?
Severe disease with fewer worms
Describe heartworm disease in dogs
Cardiopulmonary
Primary due to adults in pulmonary arteries
Narrowing/occlusion of pulmonary arteries
Disrupts intima
Leads to pulmonary hypertension
What does pulmonary hypertension cause?
Dilation of right ventricle
Compensatory myocardial hypertrophy
What occurs with congestive heart failure?
Ascites
Hydrothorax
Hydropericardium
What can parasites in the heart do?
May trigger mechanical valvular damage/endocarditis
What is the progression of clinical signs with heartworms in dogs?
Early: Inapparent
Mild: Cough
Moderate: Cough, exercise intolerance, abnormal lung sounds
Severe: Dyspnea, hepatomegaly, syncope, ascites, abnormal heart sounds, death
What is the approved heartworm treatment?
Adulticide therapy
What is used in adulticide therapy?
Melarsomine dihydrochloride
What is used as a preventive for heartworms?
Macrocylic lactones
What is adulticide theapy effective on?
Worms greater than 4 months post-infection
What are macrocyclic lactones effective against?
L3 and L4
What is caval syndrome?
Acute disease/clinical emergency caused by a large number of worms
Increased venous pressure
What are the clinical signs of caval syndrome?
Acute onset of weakness/anorexia Dyspnea Collapse Pale mucous membranes +/- jaundice Bilirubinemia Bilirubinuria Hemoglobinuria
What is the PPP of heartworms in cats?
7-8 months
What is the lifecycle of heartworms in a cat?
Infected mosquito takes a blood meal
L3 to enter skin
L3 molt to L4; L4 molt to adult
Adults arrive in pulmonary vasculature
What are the 2 stages of heartworm disease in cats?
When parasites arrive in pulmonary vasculature
When adult heartworms die
What are clinical signs associated with acute phase of heartworm disease in cats?
Subside as worms mature
Histopathologic lesions evident when cat clears infection
Occlusive medial hypertrophy of small pulmonary arterioles
How frequently do cats become microfilaremic?
Rarely
What is Wolbachia pipientis?
Intracellular gram-negative bacteria
What does Wolbachia pipientis play a role in?
Pathogenesis and host immune response
What is Wolbachia pipientis necessary for?
Dirofilaria immitis to reproduce/thrive
How do you treat Wolbachia pipientis?
Doxycycline
